Findings from a large international research study has reported that using faecal immunochemical tests (FIT) are almost 100% accurate at ruling out bowel cancer in patients with suspicious symptoms. The outcomes were featured in the paper, ‘Faecal immunochemical test is superior to symptoms in predicting pathology in patients with suspected colorectal cancer symptoms referred on a 2WW pathway: a diagnostic accuracy study’, published in Gut.
"NICE FIT is the largest diagnostic accuracy study ever performed of FIT in patients presenting with bowel symptoms” said Mr Muti Abulafi, Consultant Colorectal Surgeon at Croydon University Hospital, and Chief Investigator of the study. “It proves that this simple, at home test is highly sensitive and can detect bowel cancer, when present, with 97% accuracy.”
NICE FIT is the largest international research study assessing the accuracy of using a faecal immunochemical test (FIT) in ruling out bowel cancer in patients with high-risk symptoms. The aim of the study was to establish the diagnostic accuracy of FIT in symptomatic patients referred with suspected colorectal cancer under the current NICE guidelines.
Recruitment began in October 2017, and when recruitment finished in April 2019, 25,000 patients from 55 hospital sites in England were invited to participate in the trial, and 9822 patients with colonoscopy outcomes were included in the final data analysis. The study was completed in January 2020.
The results showed that the prevalence of colorectal cancer at colonoscopy was 3.3%. The FIT positivity decreased from 37.2% to 19.0% and 7.6%, respectively, at cut-offs of 2, 10 and 150 µg haemoglobin/g faeces (µg/g). The positive predictive values of FIT for CRC at these cut-offs were 8.7% (95% CI, 7.8% to 9.7%), 16.1% (95% CI 14.4% to 17.8%) and 31.1% (95% CI 27.8% to 34.6%), respectively.
The negative predictive values were 99.8% (95% CI 99.7% to 99.9%), 99.6% (95% CI 99.5% to 99.7%) and 98.9% (95% CI 98.7% to 99.1%), respectively. The sensitivity of FIT for CRC decreased at the same cut-offs from 97.0% (95% CI 94.5% to 98.5%) to 90.9% (95% CI 87.2% to 93.8%) and 70.8% (95% CI 65.6% to 75.7%), respectively, while the specificity increased from 64.9% (95% CI 63.9% to 65.8%) to 83.5% (95% CI 82.8% to 84.3%) and 94.6% (95% CI 94.1% to 95.0%), respectively. The area under the receiver operating characteristic curve was 0.93 (95% CI 0.92 to 0.95).
In summary, they researchers noted that a FIT test is effective at ruling out colorectal cancer with 99.8% accuracy, whilst at the same reducing the need for invasive investigations and a visit to the hospital in approximately 60% of patients with a negative FIT result.
“FIT will certainly revolutionise the way we manage patients with suspected bowel cancer symptoms,” added Abulafi. “I cannot thank enough everyone who made this research a reality, above all the thousands of patients who volunteered to take part.”
The study has shown FIT to be as sensitive a test as colonoscopy, which is currently the gold standard for detection of colorectal cancer. Therefore, the evidence generated from the study shows that FIT can potentially significantly reduce the number of colonoscopies undertaken, by identifying those who do not require the invasive test.
''Our results show that FIT is essentially a very accurate home test for bowel cancer. If the test is negative in patients with symptoms, the chance of being cancer free is 99.8%,” said Mr Nigel D'Souza, Colorectal Surgical Fellow, who supported the NICE-FIT clinical trial during his research fellowship at Croydon University Hospital. “This test can be performed at home without needing to visit hospital or even your GP, which is particularly useful during this time of coronavirus. This study was unprecedented in its scale, and the results have undoubtedly transformed bowel cancer outcomes and care for patients with bowel symptoms in England."
Further analysis of the dataset is being undertaken to examine the sensitivity of FIT at diagnosing other colorectal conditions.
The study was supported by RM Partners, the West London Cancer Alliance hosted by The Royal Marsden with funding from NHS England's cancer transformation fund.
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